General histology.(introduction)

1. General Histology

2. Histology definition
is the study of the tissues of the body
and how these tissues are arranged
to constitute organs. The Greek root
  histo can be translated as
either "tissue" or "web," both of
which are appropriate because
tissues are usually webs of
interwoven filaments and fibers,
both cellular and non cellular, with
membranous linings. Histology
involves all aspects of tissue biology

3. Why is histology important ?
It is important because it is one
of the tools in the medical
toolbox for diagnosis of
diseases. A great many
diseases reveal themselves at
the cellular level: many
cancers, bone and connective
tissue diseases, vascular
diseases, liver diseases, kidney
diseases and others can be
definitively diagnosed using
histological techniques.

4. General information
. Tissue = Cells with similar structure &
function organized into groups or layers
. Levels of cellular organization are:
Cells>tissue>organ>system>organism
. Four major types of tissues:
Epithelial (Covers or lines surfaces,
found in glands(
Connective (Bind & support body
parts(
Muscle (Movement(
Nervous (Detect changes & transmit
info.(

5. I-Epithelial tissue
characteristics of epithelial tissue
Covers all body surfaces( inside & outside(
•Free surface & basement membrane =basal lamina
which is (connective tissue(
High rate of cell division (healing(
vascularity (rely on diffusion(
Many tightly packed cells, usually arranged into layers

6. Epithelial tissue that occurs on the interior surfaces of the
body is known as endothelium .
small amount of intercellular substance
The basement membrane  provides structural
support for the epithelium and also binds it to
neighbouring structures.
Form glands ,part of sense organs & germinal structures
Function:-
Protection – epidermis of skin
Secretion_ glands
Sensory _neuroepithelium in taste buds
Contraction _ myoepithelium
Reproduction _germinal epithelium

7. Origin:_
Ectodermic – skin epithelium
Endodermic_ gut epithelium
Mesodermic_ urinogenital
epithelium

9. Classification of epithelium according to
structure & function
I_ covering epithelium
II_ glandular epithelium

10. Covering epithelium
According to no of layers :-
Simple epithelium= one layer
Stratified // > one layer
According to shape of cells:-
Squamous… like scales ,polyhedral,oval
central nucleus
Cuboidal … like cube,spherical central
nucleus
Columnar …oval basal nucleus

11. Simple epithelium
1- simple squamous epithelium around blood vessels,
covering heart, lining body cavities
Function: diffusion
2-simple cubical epithelium collecting tubules of kidney
Function ion exchange
3- simple columnar epithelium intestine
Function absorption
4- simple ciliated columnar epithelium oviduct
5-pseudostratified columnar vasdefrense
6-pseudostratified ciliated columnar trachea

13. Stratified epithelium
1-Stratified squamous epithelium
keratinized, on-keratinized) ex-epidermis of
skin
Keratinized non-keratinized

14. 2-stratified cuboidal epithelium
Ex-duct of sweat gland

15. 3-stratified columnar
epithelium
Ex- epiglottis

16. Transitional epithelium
Ex-lining of urinary bladder

17. Glandular epithelium
acc to no of cells
Unicellular multicellular
Ex- goblet cell ex-sweat gland

18. Acc to presence or absence of
duct
Endocrine-thyroid gland
Exocrine- sweat gland
Mixed- pancreas

19. Acc to method of secretion
Merocrine -secretory cells remain
intact, discharge by exocytosis- ex-
pancrease
Apocrine-apical part of glandular cell
detaches with secretion- ex-
mammary gland
Holocrine-glandular cell burst-ex-
sebaceous gland

20. Classification of glands acc to
shape of secretory portion
1-tubular (intestinal glands(
2-alveolar (poisonous gland in skin of toad(
Tubulo-alveolar (salivary gland & pancreas(
Classification of glands Acc to duct system
)A) Simple :-
Simple tubular gland (ex) intestinal gland
Simple coiled tubular (ex) sweat gland
Simple branched tubular (ex) sebaceous gland of human skin
Simple alveolar (ex) mucous& poisonous gland in skin of toad
)B) compound:_
compound tubular (ex) kidney
Compound alveolar (ex) mammary gland
Compound Tubulo-alveolar (ex) pancreas

21. Special types of epithelium
1- neuroepithelium (ex) taste buds
2-germinal epithelium (ex) testis& ovary
3-myoepithelium (ex) lining of glands
Polarity of epithelium
Cilia for movement
microvilli

22. Next
Connective
tissue